Acoustic Characterization of a Direct Field Acoustic Testing Source

Acoustic characterization measurements of a large sound source have been carried out in reverberant and hemi-anechoic rooms. The source and its associated amplification and control systems are designed for high intensity direct field acoustic testing applications. The objectives of the tests were to measure the sound power output and sound radiation directivity of the source for various excitation settings and to investigate the acoustic scattering effect created by the source structure. For sound power calculations, both a room acoustic and an intensity-based method were utilized. To investigate radiation directivity and source scattering effects, the source was placed in a hemi-anechoic room and two vertical microphone arrays were roved along an arc for sequential sound field acquisitions. A separate volume velocity source was positioned in the hemi-anechoic room to measure acoustic pressure to volume velocity transfer functions at response points in the vicinity of the source. Source power draw, including current and voltage time histories, were also measured during these tests to develop transfer functions relating acoustic power output to electrical power input. Data resulting from these tests are suitable for source model calibration and refinement to improve the accuracy of future direct field acoustic test simulations. The test procedures and measurement results are described herein.